Abrading material and process for preparing the same



Jan. 8, 1935.

T. POHL ET AL ABRADING MATERIAL 'AND PROCESS FOR PREPARING THE SAME IFiled Feb. 20, 1932 gwuentoc Eeadorfo/z Z azzzZJaag/JZ- :zezhbz: W' vQmPatented Jan. 8, 1 935 PATENT OFFICE ABRADING MATERIAL AND PROCESS FORPREPARING THE SAME TheodorPohl, Frankfort-on-the-Main, and JosefSchneider, Oberursel-on-the-Taunus, Germany Application February 20,1932, Serial No. 594,304

In Germany February 26, 1931 r 11 Claims. ((11,. 51-280) This inventionrelates to abrading materials for use in abrading andgrinding'op'erations.

divided portions of relatively hard materials held together in asuitable working form by a binding agent. Among the abrading materialsfrequently employed for such purposes arecarborundum, eorun'dum, andfinely-ground glass. As binders for the abrading material self-hardeningmaterials such as gypsum, cement, low-melting glass and similarsubstances have been used and also materials which are notself-hardening themselves but which may be hardened by heating, dryingor suitable chemical treatment such as, for example, dextrin, glue,albumins, caseins and similar materials; In certain cases, it has beenfound desirable and advantageous to use the combination of two or moreof the binding agents.

The selection of the particular grinding material In the finishedproduct heretofore known, the

hard particles of the abrading material are compactly held together bythe binding materials, the mass containing very irregular and minutepores or spaces which unavoidably developed during the preparationthereof. The abrading composition has been made to' assume manydifferent forms, such as slabs, sticks and wheels in which it may beconveniently utilized; 1

Prior abrading compositions and devices, formed of the materials and inthe general manner described, have had the serious disadvantage thatafter a comparatively short use the attacking power'or the abradingeffect on the work being treated rapidly diminishes. This diminution ofthe abrasive action has been duev to the fact that the fine pores whichexist within the composition mass'become clogged and covered with the material removed from the work treated and, as a consequence, the. surfaceof the abrading ma-,'

terial tends to become smooth and ineffective.

A further disadvantage of prior abrading compositions and devices of thecharacter referred to an abrasive substance which will maintain itscutting and abrading efliciency throughout its life and continuouslypresent an attacking or cutting surface of predetermined power'andeffectiveness.

A still further object of the invention is to provide an abradingmaterial which, when formed into grinding discs or wheels, will becomevery much less heated when rotated at high speeds than grinding discsheretofore known, and which will thereby avoid damage to the materialbeing worked, such as by burning or melt- Another object of theinvention is to provide a grinding material and articles formed thereofwhich has a comparatively coarse cellular formation and in which theparticles are spaced a RHSSUW greater distance apart than in thoseheretofore known.

Still another feature of the invention resides in an, improved ,andnovel method for producing abrasive materials and articles madetherefrom. These and other features of the invention, and the novelmethod referred to, will be more fully apparent from the followingspecification when read in conjunction with-the annexed drawing and willbe particularly pointed out in the appended claims.

In the drawing: Fig. l is a side view of an abrading disc formed fromthe abrading material of this invention. Fig. 2 is a section along line2--2 of Fig. 1. Figs. -3, 4, 5, 6 and '7 are modified forms of abradingdiscs constructed in accordance with the particles of the abradingmaterial or to the mixture of the abrading and binding materials areadded compounds which act either in conjunction with the liquid employedto render the mass plastic or under the influence of other materials toliberate gases. Suitable compounds which may be added to theabrasive-binder plastic mass for this purpose are aluminum, calcium,magnesium or alloys of these metals, zinc, calcium carbide andbicarbonate. If necessary, certain alkali compounds may also be added tostimulate gas' liberation.

A satisfactory method of obtaining the desired coarse porous cellularstructure is to add oxygen bearing compounds .such as hydrogen peroxide(H202) to the mass of grinding and binding materials. The hydrogenperoxide may be used in either liquid or-solid form. Iiibera'tion of theoxygen may be stimulated by the addition of a catalyst, such asmanganese dioxide or copper powder, or by suitable chemicals or by heat.An

important advantage of this particular process is that it is possiblethrough it to regulate, or at least greatlyinfluence, the size of thepores or cells which are formed.

.As examples of the described method, the following have yielded highlysatisfactory results:

Example 1 Nine kg. of powdered'glass of suitable fineness are mixed in adry condition with 1 kg. of dextrin and sumcient water is added to bringthe mixture into a plastic condition. While slowly stir-f To a heatedsolution of two kg. glue (4 parts glue=3 parts water), 400 cm. of 30%hydrogen peroxide (H202) are rapidly added. The resulting mass isintimately mixed, by stirring, with the catalyzer which may be a mixtureof 30 g.

of finely pulverized manganese dioxide in 300 cm. of water. As thedevelopment of oxygen begins, the mass is converted into a-tough batchinto which is added 9 kg. of powdered glass which has been moistenedwith water and preheated, the addition taking place during stirring.Thereafter, the mass poured into suitable forms. After cooling, it isremoved'from the forms, dried and solidified.

Example 3 Five kg. of a very finely pulverized glass havingan extremelylow melting point is stirred with 2.3 litres of water and 150 cm. of 30%hydrogen peroxide (HzQa) and 0.5 litres of ,a 2% soap solution Asacatalyzer, 25 kg. of manganese dioxide dissolved in 250; cm. of. waterare added. The addition of the catalyzer causes the development andrelease of the gas which results in an enlargement of the mass. Whilethe mass is being stirred,

5 kg. of agrinding material suchas ground glass of an extremely highmelting point or silicon carbide; are added. The resulting. mixture ispoured into" suitable forms and dried... It is then heated until the lowmelting components of the mixture have sintered.

Example 4 A solution containing 2 kg. of glue is prepared, having theproportions of 2 partsglue to 3 parts water. The solution is heated andcm? of 30% hydrogen peroxide (H202) are added thereto. While thismixture is being stirred, 5 kg. of crystal glass powder which has beenmoistened with 750 cm. of water are added. To stimulate the developmentand release of gas, 25 g. of manganese dioxidesuspended in 250 cm. ofwater to rise. The

are employed. Whenthe gas development has begun, 5 kg. of a grindingmaterial such as powdered carborundum, or corundum, are stirred into themass. While still warm, the mass is poured into suitable forms, driedand thereafter heated 5 until the glass powder, acting as a binder, has

sintered.

Example. 5

solid bakelite powder which has been previously The batch is" thoroughlymixed and thereafter poured into moistened with 1 litre of water.

suitable forms. After drying, the resulting prodnot is saturated with asolution of bakelite in ace tone After being further dried, the productis preferably heated under pressure to between -170" C.

Example 6 One thousand g. of a suitablegrinding material, such as glasspowder, are mixed and stirred with 150 g. df liquid bakelite. Into thismass, 5 cm. .of hydrogen peroxide (30%),, diluted with 10 cm. ofacetone, are stirred. 5 g. of manganese dioxide dissolved in 25 cm. ofacetone is thenadded and stirred intdthe mixture; The resulting mass ispoured into forms where it is allowed mass is thereafter dried andhardened.

Example 7 A solution is made of 2 kg. of glue in the. proportion of 4parts of glue to 3 parts of water. In this solution is thoroughly mixed9 kg. of finely ground emery which has been previously mois'-. tenedwith 1 litre of water. When a uniform mixture has been obtained, 400 cm.of hydrogen peroxide solution (30%) are added and well stirredtherewith. A mixture of 30 g. of manganese dioxide in 300 g. of water isnext added.

'After swelling of the mass due to the released oxygen, the mass isplaced into suitable forms. While still in a wet condition, the formedproduct is subjected to formaldehyde vapors which causes solidification.The product is then dried. Thereafter, the product may be furthertreated by dipping'into solutions of. resins or caoutchouc or abakelite-acetone solution. After a-final drying operation, the productis ready for use.

The coarse cellular or porous formation of the character contemplated bythe invention may .also be obtained "by mechanically stirring or beatinga plastic mixture of the grinding and binding materials in a violentmanner. The result of this agitation is the production of a lightfoam-like mass which, upon hardening, will have the desired cellularformation. This treatment "may be advantageously improved by theaddition of foam-forming compounds.

Example 8 A Nine kgjo'f glass frits which have been moistened withapproximately, 1.4 litres of water are thoroughly stirred with asolution of 2 kg. of glue,

containing 4 parts of glue and 3 parts of water. Into this powderedglass-glue mixture, 4 kg. of

kaolin foam are stirred, the kaolin foam used being produced as follows:4 kg. of kaolin are stirred into a uniform solution with 3.2 kg. ofwater. To

this solution is added a mixture of 1000 g. of

kaolin or clay and 40 g. of aluminum powder which have been dispersed in1000 cm. of water,

- kaolin foam with the glass-glue mixture isplaced in forms andsubsequently solidified and tempered by treating with a formaldehydesolution or with formaldehyde vapors. If desired the product may thenalso .be. impregnated with rubber or bakelite solution.

Example 9 A solution is prepared by dissolving 60 g. of, glue in 240 g.of water. The solution is beaten and stirred for a considerable timeuntil a viscous foam has been produced. Into this glue foam are stirred450 g'. of carborundum powder of seorganic materials, having dimensionscorresponding to those of the cells to be produced are added to andthoroughly mixed with the plastic mass which comprises the abrading andgrinding materials. After the mass has solidified, either temporarily orfinally, the added solid bodies are removed by appropriate treatment andleave the empty cells or pores throughout the mass. The method ofremoval will of course depend upon the nature of the solid materialemployed, and also to some extent upon the binding materials used. Thus,if sodium chloride and sugar are employed as the solid to form-thecells, removal is effected by lixiviation with water. Saw dust would beremoved by burning. Melting and evaporation may also be resorted to forremov-.

ing solids of other'types.

Example 10 Threehundred and thirty g. of carborundum N0. 46 (with avolume of about 0.01 mm?) are covered with approximately 60 g. of asolution of bakelite so that the carborundum grains become The sugarpearls are then loosened from the mass with hot water, the productdried' and subsequently impregnated with liquid bakelite. The product isthen hardened. The hollow cells interspersing the product areapproximately" the finishing treatments following the cell-producingsteps. It is frequently advantageous to impregnate or saturate thecellular material with such substances as lac, resins, artificial andsynthetic resins, such as bakelite, caoutchouc dispersions, caoutchoucsolutions and glue, shellac or water glass. As a final step, thematerial is dried, heated, hardened, chemically treated or vulcanized inaccordance with the needs of the material or the nature of the productdesired.

The abrading compounds produced by the invention are interspersed withsubstantial and preferably uniformly formed cells or holes which areseparated from each other by solid walls of the abrading mixture; thewalls themselves bein substantially free from pores or cells. The cellsor holes can be of various shapes, such as, balllike, cylindrical, etc.,and the size may vary within a wide range. The form and size of thecells Whatever the method by which they are formed,

and regardless of the size thereof which may vary through a considerablerange, it is important that the size of the pores or cells should beeither equal to or a multiple of the size of the particles of abradingmaterial used. If this relationship between the cells and the abradingsubstance is observed, the material removed from the work being treatedand the loosened and brokenparti cles of the abrading materialarepermitted to escape from the cells and thus leave the latter free andunclogg'ed. As a result, the abrading material at all times presents anactive surface consisting of sharp and relatively narrow cutting edgesformed by the walls of the cells or pores. j

The following table indicates the various multiples which may beadvantageously applied between the volume of the cells and the grindingmaterials, when the cells are ball-shaped:

(il igitigiiglg Middle vol. Multiple oi tlis gli'gigeigglume of a ballgranulation 29 The appended drawing illustrates certain specific formsof cellular formation which may be given to the abrading compositions,the material in each instance being illustrated in the form of agrinding disc. According to Figs. 1 and 2, the grinding disc 2 has ahoney-comb formation wherein the hollow cells 4 are uniformlydistributed throughout the entire disc, the cells being surrounded bythe comparatively thin walls 6 of the selected abrading and bindingmaterial. The. cells extend from the periphery of the disc inwardly tothe axis opening 8 and from one side to the other. The cells aregenerally cylindrical or ball-shaped.

In Fig. 3, the grinding disc is characterized by hollow rectangularcells 10 separated from each other by the walls 12 of abradingcompositions, the walls andcells forming a general honey-comb formation.The hub 14 of the disc and a central zone 16 are madeof the sameabrading composition as the walls 12 but are substantially solid anddevoid of cells.

According to Fig. 5, the grinding disc is pro;

vided'with transverse bores 22 arranged parallel to the axis andextending through the. entire thickness 01 the disc from one side to theother.

- The center of the disc is formed by the solid zone 24. The bores arearranged generally in circles, the circumference of which becomes largeras the distance from the axis of the disc increases.

In Fig. 6, the disc is formed with radially extending prismatic bores 28generally similar to those of Fig. 4, and has a solid area of abrasivecomposition 28 similar to the disc of Fig. 3. Fig. 7 illustrates a'grinding disc in which the cells 30 vary insize and formation but arerelatively' large as compared with the grains of the abrading materialof the surroundingcomposk tion 32.

The cells of thediscs may be formed by 'any of the methods hereinbeforedescribed, while bores of the type, shown in Figs. 4, 5 and 6 may beformed by punching or boring while the disc is in plastic orsemi-plastic conditionand prior to the setting or hardening of. thematerial.

An 'abrading disc formed in accordance with the present invention hasmany advantages over previous grinding discs. As the abrading compoundswear away, new hollow cells continucusly open. In this manner, new andfresh cutting edges are continuously presented. As the hollow spaces orcells are substantially large as compared with the grindingparticlesremoved from thematerial being treated, they do not become clogged but,on the contrary, are always free of extraneous matter. Thejgrindingefllciency or attacking powerof the disc does not diminish with With anabrading device constructed in accordance with the invention it ispossible to grind and .abrade many materials which heretofore could betreated only by means of fresh sand, or emery paper, or cloth. Thus, itis now possible to grind'eifectively materials such as wood,-

cork, and leather. Other materials. which may be effectively treated bythe abrading device of this invention are, ebonite, galalith, celluloid,glass, ceramic materials, such as chamottes, porcelain and the like,molten magnesia, aluminum oxide, and metals and metal alloys such as,"

brass, bronze, steel and the like.

Having thus described the invention what we claim as new and desire tosecure byLetters Patent of the United States is: 1. As an article ofmanufacture, a grinding body of cellular structure consisting ofabrading and binding materials and having hollow spaces uniformlyinterspersed throughout, said hollow spaces being larger than the grainsof the abrading material used.

p ployed.

2. As an article of manufacture, a grinding bodyotbellular structureconsisting of abrading nd binding materials'and having hollow spacesuniformly interspersedthroughout, said hollow spaces being ofsubstantially uniform size and larger than the grains of the abradingmaterial 3.'As an article of manufacture, a grinding body of cellularstructure consisting of abrading .and binding materials and havinghollowspaces uniformly interspersed throughout, the avera'ge uniformlyinterspersed throughout, said hollow spaces being larger than the grainsof the abradmaterial .used, the individual cells forming saidhollowspaces being spaced from each other.

by thin walls consisting of the grinding and binding materials.

5.-As an article of manufacture, a grinding body of cellular structureconsisting of abrading and binding materials andhaving hollow spacesuniformly interspersed throughout, said hollow spaces being larger thanthe grains of the abrading material employed, the individual cellsforming said hollow spaces being partially separated from each other. 6.A grinding body consisting of abradingrmaterial and binding medium, andhaving therein pores of greater size than the grains of theabradingmaterial, said pores comprising 50% or more of the total volumeof the grinding body.

7. A grlndingbody consisting of abrasive ma-' terial and binding mediumwhich, by being uniformly interspersed with hollow spaces, has acellular structure, and the number and size of the hollow spaces is suchthat the total volume of the hollow spaces, inclusive of any pores whichmaybe present in the walls, is 50% or more of the total volume of thegrinding body or the part of the grinding body which is interspersed byhollow spaces and the average size of the hollow spaces is at leastequal to the average size of the ains of abrasive material. Q

B. Grinding body according to claim 7 in which the total volume of thehollow spaces amounts to 60 to 80% of the total volume of the grindingbody or of the part of the grinding body inter-e spersed by artificialhollow spaces.

9. Grinding body according to claim 7, in which nected by openings. ITHEODOR POHL. JOSEF SCHNEIDER.

the size of the grinding grains

